ML20135B436

Requests Addl Info Re Offsite Power Sys Designs for Older Operating Plants as Result of Lessons Learned from Maine Yankee Independent Safety Assessment

ML20135B436
Person / Time
Site:	Vermont Yankee
Issue date:	02/25/1997
From:	Rooney V NRC (Affiliation Not Assigned)
To:	Reid D VERMONT YANKEE NUCLEAR POWER CORP.
References
TAC-M97960, NUDOCS 9703030047
Download: ML20135B436 (5)

Text

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February 25,,1997'

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,s Mr. Donald A. Reid .

' s Vice President, Operations' '

Vermont Yankee Nuclear Power Corporation--

Ferry Road .

Brattleboro, VT 05301 ~

SUBJECT:

VERMONT YANKEE NUCLEAR POWER STATION (TAC NO. M97960)

Dear Mr. Reid:

The NRC staff is reviewing offsite power system designs for older operating

, plants as a result of lessons learned from the Maine Yankee Indepenent Safety Assessment. We find that additional information is necessary to complete our review for Vermont Yankee.

Your response to the enclosure to this letter is requested as soon as possible but no latar than 30 days from the date of receipt of this letter. If you have questions regarding the enclosure or are unable to meet the requested response date, please call me at (301) 415-3045, or e-mail me at vir0nrc. gov.

Sincerely, (Original Signed By)

Vern n L. Rooney, Senior Project Manager g k hh h.nDV us a Project Directorate 1-3 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation Docket No. 50-271 Distribution Docket File Slittle

Enclosure:

Request for Additional Information PUBLIC THarris (e-mail)

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a aes;g L' g 1 UNITED STATES '

s* j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30666 0001 o i s'*4 , , .ol February 25, 1997 l i

Mr. Donald A. Reid Vice President, Operations Vermont Yankee Nuclear Power Corporation Ferry Road Brattleboro, VT 05301 t l

SUBJECT:

VERMONT YANKEE NUCLEAR POWER STATION (TAC NO. M97960)

Dear Mr. Reid:

The NRC staff is reviewing offsite power system designs for older operating  !

plants as a result of lessons learned from the Maine Yankee Indepenent Safety t Assessment. We find that additional information is necessary to complete our review for Vermont Yankee.

Your response to the enclosure to this letter is requested as soon as possible but no later than 30 days from the date of receipt of this letter. If you have questions regarding the enclosure or are unable to meet the requested response date, please call me at (301) 415-3045, or e-mail me at virenrc. gov. ,

l Sincer y l

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Vernon L. Rooney, Senior Project Manager Project Director e I-3 Division of Reactor Projects - I/II i Office of Nuclear Reactor Regulation '

' Docket No. 50-271

Enclosure:

Request for Additional Information cc w/ encl: See next page

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Vermont Yankee Nuclear Power Vemont Yankee Nuclear Power Station i Corporation

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cc: '

Mr. David Rodham, Director Regional Administrator, Region I ATTN: James Muckerheide  ;

U. S. Nuc1sar Regulatory Commission Massachusetts Civil Defense Agency i 475 Allendale Road 400 Worcester Rd. i 4

King of Prussia, PA 19406 P.O. Box 1496 '

Framingham, M 01701-0317

. Ropes & Gray Mr. Raymond N. McCandless One International Place Vermont Division of Occusational ,

Boston, M 02110-2624 and Radiological Healti Administration Building Mr. Richard P. Sedano, Commissioner Montpelier, VT 05602 l Vermont Department of Public Service  !

120 State Street, 3rd Floor Mr. J. J. Duffy l Montpelier, VT 05602 Licensing Engineer '

Vermont Yankee Nuclear Power Public Service Board Corporation

, State of Vermont 580 Main Street 120 State Street Bolton, M 01740-1398 1 Montpelier, VT 05602 i Mr. Robert J. Wanczyk, Plant Manager 1 Chairman, Board of Selectmen Vermont Yankee Nuclear Power Station l Town of Vernon P.O. Box 157, Governor Hunt Road l P.O. Box 116 Vernon, VT 05354 l Vernon, VT 05354-0116 Mr. Ross B. Barkhurst, President Mr. Richard E. McCullough Vermont Yankee Nuclear Power Operating Experience Coordinator Corporation i Vermont Yankee Nuclear Power Station Ferry Road P.O. Box 157 Brattleboro, VT 05301 Governor Hunt Road Vernon, VT 05354 3 G. Dana Bisbee, Esq.

Deputy Attorney General 33 Capitol Street Concord, NH 03301-6937 Resident Inspector Vermont Yankee Nuclear Power Station U.S. Nuclear Regulatory Commission P.O. Box 176 Vernon, VT 05354 Chief, Safety Unit j Office of the Attorney General One Ashburton Place, 19th Floor Boston, M 02108 j I

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I REQUEST FOR ADDITIONAL INFORMATION REGARDING THE ADE00ACY OF THE [ELAYED OFFSITE POWER CIRCUIT j VERMONT YANKEE NUCL MR POWER STATION ~

i The U.S. Nuclear Regulatory Commiission recently performed a review of offsite power system designs for older operating plants as a result of lessons learned from the Maine Yankee Independent Safety Assessment. The review was conducted to verify the: adequacy of delayed offsite power circuits. In particular, the staff was concerned with plants that rely upon main and unit auxiliary.

transformers to backfeed power to the onsite distribution system by removing the disconnect links between the main generator and the main transformer.

This review identified Vermont Yankee as a plant that included this feature.

1 Vermont Yankee was licensed with only one immediately avnilable offsite power j circuit and a delayed offsite power circuit that relies on a backfeed through <

the main and unit auxiliary transfomers. In o Ner to establish this backfeed the main generator disconnect. links must be removed. For a delayed offsite power circuit to be considered an acceptable source of offsite power, it must be shown that power can be reestablished in sufficient time to prevent fuel design limits and design conditions of the reactor coolant pressure boundary from bein exceeded. The Vermont Yankee Final Safety Analysis Report (FSAR) does not state how long it is expected to take to establish the backfeed, and the staff could not find any documentation on the docket to indicate that Vermont Yankee has performed an analysis to demonstrate the adequacy of this delayed offsite power circuit.

The staff is concerned that Vermont Yankee may not have performed an analysis to demonstrate the adequacy of its delayed offsite power circuit. In order to resolve this concern, please respond to the following questions:

1. Has Ver= cat Yankee Nuclear Power Corporation (VYNPC) performed an analysis to demonstrate that the delayed offsite power circuit can be established in sufficient time to prevent fuel design limits and design conditions of the reactor coolant pressure boundary from being exceeded? ,

If so, provide a summary of the analysis and any conclusions (e.g.,  !

adequacy of time limits and voltages, etc.). l

2. Does VYNPC have procedures in place for implementing the delayed offsite power circuit when needed, and has VYNPC ever tested its capability to backfeed power within an allowable time limit? If so, how often are operators trained on using the procedures and how long does it take to  ;

establish the backfeed?

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3. It appears that Vermont Yankee FSAR and Technical Specifications (TSs) are taking credit for the Vernon Hydro line as a second delayed offsite l power circuit. Describa the analysis and acceptance criteria used by  !

VYNPC to determine that the Vernon Hydro line is acceptable as an offsite power source in view of the fact that it is used as an alternate ac power source for Station Blackout. l

4. Explain why the TSs only require one start-up transformer to be operable ,

in order to startup and operate Vermont Yankee. This TS appears to be ,

deficient since it allows Vermont YankW to operate inde'initely without '

ENCLOSURE

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an immediate source of offsite power available to one division of engineered safeguards equipment.

l l S. The staff noted that TSs do not contain surveillance requirements regarding the delayed offsite power circuit. Explain how Vermont Yankee periodically verifies its ability to establish offsite power within a specified time limit using the main and unit auxiliary transformers.

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